Materials Selection And Processing Techniques For Small Spacecraft Solar Cell Arrays, Naseem M. Torabi

Theses and Dissertations--Electrical and Computer Engineering

Body mounted germanium substrate solar cell arrays form the faces of many small satellite designs to provide the primary power source on orbit. High efficiency solar cells are made affordable for university satellite programs as triangular devices trimmed from wafer scale solar cells. The smaller cells allow array designs to pack tightly around antenna mounts and payload instruments, giving the board design flexibility. One objective of this work is to investigate the reliability of solar cells attached to FR-4 printed circuit boards. FR-4 circuit boards have significantly higher thermal expansion coefficients and lower thermal conductivities than germanium. This thermal expansion ...

Terahertz Wave Approach And Application On Frp Composites, Kwang-Hee Im, David K. Hsu, Chien-Ping T. Chiou, Daniel J. Barnard, Jong-An Jung, In-Young Yang

Center for Nondestructive Evaluation Publications and Papers

Terahertz (THz) applications have emerged as one of the most new powerful nondestructive evaluation (NDE) techniques. A new T-ray time-domain spectroscopy system was utilized for detecting and evaluating orientation influence in carbon fiber-reinforced plastics (CFRPs) composite laminates. Investigation of terahertz time-domain spectroscopy (THz-TDS) was made, and reflection and transmission configurations were studied as a nondestructive evaluation technique. Here, the CFRP composites derived their excellent mechanical strength, stiffness, and electrical conductivity from carbon fibers. Especially, the electrical conductivity of the CFRP composites depends on the direction of unidirectional fibers since carbon fibers are electrically conducting while the epoxy matrix is not ...

The Effect Of Sensor Mass, Sensor Location, And Delamination Location Of Different Composite Structures Under Dynamic Loading, Albert Darien Liu

Master's Theses and Project Reports

This study investigated the effect of sensor mass, sensor location, and delamination location of different composite structures under dynamic loading. The study pertains to research of the use of accelerometers and dynamic response as a cost-effective and reliable method of structural health monitoring in composite structures. The composite structures in this research included carbon fiber plates, carbon fiber-foam sandwich panels, and carbon-fiber honeycomb sandwich panels. The composite structures were manufactured with the use of a Tetrahedron MTP-8 heat press. All work was conducted in the Cal Poly Aerospace Structures/Composites Laboratory. Initial delaminations were placed at several locations along the ...

Inspection Of Helicopter Rotor Blades With The Help Of Guided Waves And "Turning Modes": Experimental And Finite Element Analysis, Daniel J. Barnard, Sunil Kishore Chakrapani, Vinay Dayal

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

Modern helicopter rotor blades constructed of composite materials offer significant inspection challenges, particularly at inner structures, where geometry and differing material properties and anisotropy make placement of the probing energy difficult. This paper presents an application of Lamb waves to these structures, where mode conversion occurs at internal geometric discontinuities. These additional modes were found to successfully propagate to the targeted regions inside the rotor and back out, allowing evaluation of the structure. A finite element model was developed to simulate wave propagation and mode conversion in the structure and aid in identifying the signals received in the laboratory experiment ...

Investigation Of Waviness In Wind Turbine Blades: Structural Health Monitoring, Sunil Kishore Chakrapani, Vinay Dayal, Daniel J. Barnard

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

Waviness in composite wind turbine blades was detected and characterized with the help of air coupled ultrasonics. Based on the aspect ratio, the detected marcels are either accepted or rejected. A passive structural health monitoring approach has been presented here to monitor the accepted marcels above a threshold. The fatigue life of specimen is most affected in the presence of a marcel. Hence this study focused on the damage evaluation after fatigue testing. Wavy laminate was subjected to fatigue load to investigate the fracture mechanisms near the marcel. Different types of defects were identified from this study and were used ...

Inspection And Evaluation Of Dry Fibers In Thick Composites, Vinay Dayal, Sunil Kishore Chakrapani, Daniel J. Barnard

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

This paper presents the investigation of dry fibers in thick composites. Dry fibers can be defined as lack of epoxy in localized regions. These local regions act as potential defects in thick composites under compressive loads and act as an initiation point for defects such as matrix cracking and delamination. Detection and characterization of dryness in glass/epoxy composites, with thickness greater than one inch, is presented in this paper. One inch samples with dry fibers were fabricated and tested. Detection is carried out with the help of air coupled ultrasonics in both through transmission and singled sided inspection. To ...

Qualification Requirements Of Guided Ultrasonic Waves For Inspection Of Piping In Light Water Reactors, R. M. Meyer, P. Ramuhalli, S. R. Doctor, Leonard J. Bond

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

It is anticipated that guided ultrasonic wave (GUW) techniques will eventually see widespread application in the nuclear power industry as there are several near-term and future needs that could benefit from the availability of GUW technologies. Already, GUW techniques are receiving consideration for inspecting buried piping at nuclear power plants and future applications may include several Class 1 and 2 components. To accept the results of a nondestructive examination of safety critical components, the U.S. Nuclear Regulatory Commission requires that the examinations be performed using qualified equipment, personnel, and procedures. As the use of GUW techniques becomes more frequent ...

Modeling The Effects Of Beam Size And Flaw Morphology On Ultrasonic Pulse/Echo Sizing Of Delaminations In Carbon Composites, Frank J. Margetan, Cara A. Leckey, Daniel J. Barnard

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

The size and shape of a delamination in a multi-layered structure can be estimated in various ways from an ultrasonic pulse/echo image. For example the −6dB contours of measured response provide one simple estimate of the boundary. More sophisticated approaches can be imagined where one adjusts the proposed boundary to bring measured and predicted UT images into optimal agreement. Such approaches require suitable models of the inspection process. In this paper we explore issues pertaining to model-based size estimation for delaminations in carbon fiber reinforced laminates. In particular we consider the influence on sizing when the delamination is non-planar ...

Computational Modeling Of Micro-Crack Induced Attenuation In Cfrp Composites, Ronald A. Roberts, Cara A. Leckey

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

A computational study is performed to determine the contribution to ultrasound attenuation in carbon fiber reinforced polymer composite laminates of linear elastic scattering by matrix micro-cracking. Multiple scattering approximations are benchmarked against exact computational approaches. Results support linear scattering as the source of observed increased attenuation in the presence of micro-cracking.

Equivalent Flaw Time-Of-Flight Diffraction Sizing With Ultrasonic Phased Arrays, Brady J. Engle, Lester W. Schmerr Jr., Alexander Sedov

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

Ultrasonic phased array transducers can be used to extend traditional time-of-flight diffraction (TOFD) crack sizing, resulting in more quantitative information about the crack being obtained. Traditional TOFD yields a single length parameter, while the equivalent flaw time-of-flight diffraction crack sizing method (EFTOFD) described here uses data from multiple look-angles to fit an equivalent degenerate ellipsoid to the crack. The size and orientation of the equivalent flaw can be used to estimate the actual crack size.

Thermal Vacuum Integration For Cal Poly's Space Environments Laboratory, Chelsea Barackman, Steven Jackowski

Aerospace Engineering

The purpose of the senior project is to construct a thermal vacuum by utilizing a preexisting vacuum chamber in the Space Environments Lab, and a donated Advanced Thermal Sciences (ATS) chiller. While a thermal vacuum is already available on campus, building one for the Space Environments Lab would grant undergraduates access to the equipment, allowing a much better understanding of testing methods and procedures in use by the aerospace industry. This paper explains the design and analysis of the thermal vacuum (T-VAC) project as well as the operation and procedures required for the ATS chiller and fill/drain tank. The ...

Two-Stage, High-Altitude Rocket With Internal Skeleton Design Entered In Advance Category Of 7th Esra Irec, Samuel S. Bowman, Kevin J. Byrne, Allen Capatina, Aliki S. Loper-Leddy, Joshua A. Van Schoyck

Aerospace Engineering

A high-altitude, two-stage rocket was designed, built, and entered in the advanced category of the 7^th Annual Experimental Sounding Rocket Association (ESRA) Intercollegiate Rocketry Engineering Competition (IREC). The rocket, called AJAKS, featured an internal skeleton made of carbon fiber rods, and a combination of plywood, carbon, and aluminum bulkheads. Loads were driven through the internal structure, with an outer skin tube providing an aerodynamic surface. A unique separation device was developed to ensure proper stage separation. The competition required the rocket to carry a 10-lb payload, which was chosen by the team to consist of an IMU and data ...

Elastic–Plastic Analysis And Strength Evaluation Of Adhesive Joints In Wind Turbine Blades, Yi Hua, Ananth Ram Mahanth Kasavajhala, Linxia Gu

Mechanical & Materials Engineering Faculty Publications

The objective of this paper is to investigate the performance of adhesive joints of carbon/epoxy wind turbine blade subjected to combined bending and tension loadings through finite element method. The influence of adhesive material properties and geometrical details including fillet and imperfections was examined in terms of interlaminar stresses in the adhesive layer. The variation of stress intensity with change in adhesive shear modulus has also been investigated, while contour integral method was used for evaluating the stress intensity factors (SIF) at the imperfection tip. Furthermore, the strength of the joint was assessed through the crack initiation and propagation ...

Effects Of Seawater On The Mechanical Behavior Of Composite Sandwich Panels Under Monotonic Shear Loading, Thomas Robert Woo

Master's Theses and Project Reports

Abstract

Salt water environments are very harsh on materials that are used within them. Many issues are caused by either corrosion and/or internal degradation to the materials themselves. Composites are better suited for this environment due to their high strength to weight ratios and their corrosion resistance, but very little is known about the fracture mechanics of composites. The goal of this study is to gain a better understanding for the behavior of a composite boat hull under a shear loading, similar to the force water applies on the hull as the boat moves through the water; then attempt ...

Manufacturing Processes In An All-Aluminum Airframe, Stewart Mcdougall

Aerospace Engineering

One often overlooked aspect to building an aircraft is the manufacturing process used to put it into production. This may be a major contributor to acquisition cost and requires a large amount of money to implement. Once all the tooling has been purchased, one of the greatest costs is labor. The experience of building an all-aluminum aircraft shows that the production process is one which may be done in many different ways. Minimizing the assembly time is important for aircraft manufacturers and one of the best ways to do that is on the assembly line itself. Specific practices in the ...

Performance Effects Of Damage Arrestment Devices On Sandwich Composite Beams Under Monotonic Loading, Yvette Vanessa Wood

Aerospace Engineering

Face-core delamination has become a subject matter in the Aerospace industry, as it can lead to early failure. In this study, sandwich composite beams are tested initially with no delamination to obtain the ultimate strength. A second case of delamination in the center of the beam in initialized to verify a decrease in ultimate strength. This experiment investigates the performance effects of the addition of Damage Arrestment Devices (DADs), in composite sandwich beams. The performance criterion is measured by strength in flexural loading test. The objective of this project is to verify an increase in the strength and performance with ...

A Study On Organic Epoxy And Hemp Composite Plates With An Emphasis On Mechanical And Finite Element Analysis, Alma Melendez

Aerospace Engineering

Several vibration and tensile tests were conducted for four natural fiber hemp composites in order to observe its behavior and acquire the material properties of hemp. Two plates were made on the Cal Poly press table, while the other two plates were made on the Cal Poly vacuum table. All four plates are made of 100% hemp under three different types of weave. The first plate is called CTPT-12, has a thickness of 0.053 inches, and was made on the press table. The second plate is called CTL4 with a thickness of 0.152 inches and made on the ...

Development Of A Pyrotechnic Shock Simulation Apparatus For Spacecraft Applications, Joseph Binder, Matthew Mccarty, Chris Rasmussen

Aerospace Engineering

This report details the research, design, construction, and testing of a pyrotechnic shock simulation apparatus for spacecraft applications. The apparatus was developed to be used in the Space Environments Lab at California Polytechnic State University. It will be used for testing spacecraft components with dimensions up to 24”x12”x12” as well as CubeSats. Additionally, it may be used as an instructional or demonstrational tool in the Aerospace Department’s space environments course. The apparatus functions by way of mechanical impact of an approximately 20 lb stainless steel swinging hammer. Tests were performed to verify the simulator’s functionality. Suggestions ...

A Resistance Based Structural Health Monitoring System For Composite Structure Applications, Dennis N. Boettcher

Master's Theses and Project Reports

This research effort explored the possibility of using interwoven conductive and nonconductive fibers in a composite laminate for structural health monitoring (SHM). Traditional SHM systems utilize fiber optics, piezoelectrics, or detect defects by nondestructive test methods by use of sonar graphs or x-rays. However, these approaches are often expensive, time consuming and complicated.

The primary objective of this research was to apply a resistance based method of structural health monitoring to a composite structure to determine structural integrity and presence of defects.

The conductive properties of fiber such as carbon, copper, or constantan - a copper-nickel alloy - can be utilized as ...

A Review Of Cutting-Edge Techniques For Material Selection, Noori Brifcani, Richard Day, David Walker, Suzanne Hughes, Ken Ball, Dave Price

Aeronautical Engineering

Selecting the optimum material for a given application is a complex task for engineers and designers across all industrial fields. There are a huge number of materials now available with a range of different properties and behaviours and so it has become even more necessary to carry out a systematic process in order to screen and/or rank the materials to give a promising number of candidates. The output of the material selection process depends upon which method is used. In some methods, a chart can be used to identify promising candidates whereas in others a single ‘optimum’ material may ...